BIOS

Pot use by teens damages brain: study

The effects of daily cannabis use on teenage brains is worse than originally thought and the long-term effects appear to be irreversible, new research from McGill University suggests.

The study, by Dr. Gabriella Gobbi, a psychiatric researcher from the Research Institute of the McGill University Health Centre, suggests that daily cannabis consumption can lead to depression and anxiety.

The new study, published in Neurobiology of Disease, suggests that the reputed "soft" drug has an impact on serotonin and norepinephrine, compounds which help control mood and anxiety.

Her research team observed that 18 rats exposed to cannabis had decreased levels of serotonin, which affects mood; and higher levels of norepinephrine, which makes one more susceptible long-term to stress.

"These permanent changes in the brain are also linked to certain mental illnesses, like schizophrenia," Gobbi said in an interview Thursday.

"And we showed that even if we stopped the cannabis use at the end of adolescence, the changes were still detectable in adulthood."

While past epidemiological studies have shown how cannabis consumption can affect behaviour in some teenagers, Gobbi said the new study demonstrates that the effects are more devastating in teens compared to adults.

"Our study is one of the first to focus on the neurobiological mechanisms at the root of this influence of cannabis on depression and anxiety in adolescents," she said.

Gobbi says the study reveals that because serotonin and norepinephrine systems are still in development during adolescence, cannabis interfere with their development.

"We don't know if some subjects would be more at-risk than others, including adults," said the McGill professor.

Gobbi said she will be observing a group of young human marijuana smokers to continue her research.